1. Technical Field
The present invention relates to a head unit arrangement method for arranging a plurality of head units in alignment with a Y-axis direction in a liquid droplet ejection apparatus for plotting an image in a matrix form with functional liquid in a number n of colors, and a liquid droplet ejection apparatus, a method of manufacturing an electro-optic apparatus, and an electro-optic apparatus.
2. Related Art
Not using this kind of head unit arrangement method, a liquid droplet ejection apparatus equipped with a plurality of functional liquid droplet ejection heads for respective colors that are arranged in the form of a staircase, a plurality of carriage units arranged in alignment with a Y-axis direction, a set table on which a workpiece is set, an X-axis table that moves the set table in an X-axis direction, and a Y-axis table that moves a plurality of head units in the Y-axis direction has been known, as described in JP-A-2005-349381. In such a liquid droplet ejection apparatus, the plurality of functional liquid droplet ejection heads for respective colors are provided so as to form a plurality of partial plotting lines (divisional plotting lines) in respective colors; a plotting process is done by repeating a primary scan in which the respective functional liquid droplet ejection heads are driven synchronously with movement in the X-axis direction, and a secondary scan in which they are moved in the Y-axis direction by the length of a partial plotting line.
For such a liquid droplet ejection apparatus to achieve efficient plotting and to plot on workpieces of a plurality of sizes, a plurality of head units having aligned thereon a plurality of functional liquid droplet ejection heads are arranged to extend in a width direction and to cover the entire area of a workpiece. Accordingly, those of the plurality of functional liquid droplet ejection heads that are positioned at both ends are used less frequently; and those two head units positioned at both ends are used less frequently than those head units positioned in the intermediate portion between the above two head units. In plotting results produced on a workpiece, a central part stands out against both sides, which tends to result in visible color variation in the central part. Accordingly, the head units which are positioned in the intermediate portion and are adapted to plot on a central part of a workpiece tend to cause occurrence of color variation.
In the above liquid droplet ejection apparatus, however, a difference in frequency of use or occurrence of color variation among respective head units is not taken into consideration, which has caused the liquid droplet ejection apparatus to involve a problem that appropriate arrangement of head units cannot be done. For example, those of a plurality of head units that exhibit high performance may be arranged at both ends on which they are used less frequently and the degree of occurrence of color variation is low, which causes a problem that accurate plotting cannot be achieved.